The invention is directed towards the field of signal detection, particularly towards signal detection circuits that differentiate between signal and noise.
Window detectors are used in applications where it must be determined if a signal falls within a specified range. In the prior art, they are implemented using two threshold comparators and two reference signals. While it the performance is device dependent, this circuit topology may only be used for signals having a frequency less than 100 MHz. The performance of the circuit is limited by the frequency of the comparators.
A window detector circuit for high frequency applications includes a differential amplifier that has two inputs which receive a differential voltage signal. A bias network, having a balancing node, is connected between the two inputs. An output transistor, electrically biased by the balancing node, is connected between power and ground.
In operation, when the differential voltage signal is below a voltage threshold, the differential amplifier is turned off and current flows through the output transistor. When the differential voltage signal is at or exceeds the voltage threshold, the differential amplifier turns on.